diff --git a/lld/MachO/OutputSegment.cpp b/lld/MachO/OutputSegment.cpp
--- a/lld/MachO/OutputSegment.cpp
+++ b/lld/MachO/OutputSegment.cpp
@@ -140,10 +140,15 @@
 }
 
 void OutputSegment::sortOutputSections() {
-  llvm::sort(sections, compareByOrder<OutputSection *>(sectionOrder));
+  // Must be stable_sort() to keep special sections such as
+  // S_THREAD_LOCAL_REGULAR in input order.
+  llvm::stable_sort(sections, compareByOrder<OutputSection *>(sectionOrder));
 }
 
 void macho::sortOutputSegments() {
+  // sort() instead of stable_sort() is fine because segmentOrder() is
+  // name-based and getOrCreateOutputSegment() makes there's only a single
+  // segment for every name.
   llvm::sort(outputSegments, compareByOrder<OutputSegment *>(segmentOrder));
 }
 
diff --git a/lld/MachO/Writer.cpp b/lld/MachO/Writer.cpp
--- a/lld/MachO/Writer.cpp
+++ b/lld/MachO/Writer.cpp
@@ -79,7 +79,10 @@
 
   LCUuid *uuidCommand = nullptr;
   OutputSegment *linkEditSegment = nullptr;
-  DenseMap<NamePair, ConcatOutputSection *> concatOutputSections;
+
+  // Output sections are added to output segments in iteration order
+  // of ConcatOutputSection, so must have deterministic iteration order.
+  MapVector<NamePair, ConcatOutputSection *> concatOutputSections;
 };
 
 // LC_DYLD_INFO_ONLY stores the offsets of symbol import/export information.
diff --git a/lld/test/MachO/tlv-dylib.s b/lld/test/MachO/tlv-dylib.s
--- a/lld/test/MachO/tlv-dylib.s
+++ b/lld/test/MachO/tlv-dylib.s
@@ -74,21 +74,21 @@
 # FLAGS-NEXT:    reloff 0
 # FLAGS-NEXT:    nreloc 0
 # FLAGS-NEXT:      type S_THREAD_LOCAL_ZEROFILL
-# FLAGS:       sectname __bss
+# FLAGS:       sectname __common
 # FLAGS-NEXT:   segname __DATA
 # FLAGS-NEXT:      addr
-# FLAGS-NEXT:      size 0x0000000000002000
+# FLAGS-NEXT:      size 0x0000000000004000
 # FLAGS-NEXT:    offset 0
-# FLAGS-NEXT:     align 2^0 (1)
+# FLAGS-NEXT:     align 2^14 (16384)
 # FLAGS-NEXT:    reloff 0
 # FLAGS-NEXT:    nreloc 0
 # FLAGS-NEXT:      type S_ZEROFILL
-# FLAGS:       sectname __common
+# FLAGS:       sectname __bss
 # FLAGS-NEXT:   segname __DATA
 # FLAGS-NEXT:      addr
-# FLAGS-NEXT:      size 0x0000000000004000
+# FLAGS-NEXT:      size 0x0000000000002000
 # FLAGS-NEXT:    offset 0
-# FLAGS-NEXT:     align 2^14 (16384)
+# FLAGS-NEXT:     align 2^0 (1)
 # FLAGS-NEXT:    reloff 0
 # FLAGS-NEXT:    nreloc 0
 # FLAGS-NEXT:      type S_ZEROFILL